Sound-amplifying system



NOV. 5, 1929. r GREEN 1,734,944

SOUND AMPLIFYING SYSTEM File'd Dec. 21, 1928 I I K U v //v VENTOQ? BY M 2 ATTORNEY:

Patented Nov. 5, 1929 1,734,944

UNITED STATES PATENT OFFICE HAROLD GREEN, OF LONDON, ENGLAND, ASSIGNOR TO GELEBRITONE LIMITED, OF LONDON, ENGLAND, A BRITISH COMPANY SOUND-AMPLIFYING SYSTEM Application filed December 21, 1928, Serial No. 327,663, and in Great Britain October 11, 1927.

This invention relates to sound amplifysound proof packing material p. Th f t ing systems and particularly to those for use cover of the casing 0 has an aperture 0 in theatres, auditoriums and the like. In for adm tting sound to-the diaphragm m such places, where an organ is frequently re- While 0i 1S an insert of felt or other soft, non- 5 quired as part of or supplementary to an orresonating material between the cover and the chestra, it may be possible to install only a diaphragm. The casing 0 is atta h d t th small reed organ because of tlie cost of a organ casing g (at the back of the organ, for large pipe organ and other considerations. instance) in such a way that the aperture 0 The present invention aims to provide coincides substantially with an aperture 0 means whereby the organ music may be amin the casing 9, through which aperture th 60 plified independently of the remainder of the sound from the organ can reach the diaorchestra so as to give results comparable phragm m. The volume of sound actually with those obtainable by the use of a large admitted to the diaphragm is regulable by i Organ means of a valve or shutter 1', which in Fig.

In accordance with my inventioml prov de 2 is shown as comprising an iris diaphragm 55 a microphone in a sound proof bo z having mechanism r Assuming this valve or shuta single small opening through which alone ter to be set normally at a medium aperture,

sound may enter from the organ at a selected provision may be made for opening it wider point where a correct balance between the when a larger volume of sound is required high and low notes is obtained. This sound to be transmitted. For this purpose Fig. 2

opening can be controlled by the organist to shows the shutter 1', r coupled by transmisregulate the volume of sound emitted through sion mechanism or cable 8 to the swells t of the amplifier. It may be accomplished autothe organ, so that when the swells are opermatically by connecting the valve, slide r ated the aperture T of the iris diaphragm other element controlling said opening with 15 simultaneously enlarged. 7 the or an swells. The placing of the micro- Referr ng now to the electrical connections phone in a sound proof box as aforesaid overof the microphone (Fig. 1) the pot magnet Z comes the difliculties due to the short disis energized by a field coil u adapted to be tance between the organ and the loud energized from a direct current source 4). The

speaker which might otherwise cause a howl moving coil to in which are generated elecso effect at a pitch determined by the resonant tric currents corresponding in frequency to points of the loud speaker and the microthe acoustic vibrations impressed on the diahon 7 phragm m is connected by leads 'w 'w to the In the accom anying drawings :-Fig. 1 input side of an amplifier, represented diais a sectional si e view of a microphone of grammatically by the thermionic valve m. the moving coil type and a sound proof en- The microphone is designed to smooth out closure therefor as adapted for carryingout the sound wave peaks, wh ch would give a "the invention, certain electricakconnectmns harsh and ready reproduction, by means of to the microphone being shown diagrammatlsuitable electrical damp ng. One convenient cally; Fi 2 is a front elevation of the apmethod consists in prov ding upon the form pa ratus 0 Fig. 1, illustrating the connection a, which carries the audio frequency moving of the device to the organ swells. coil w, a second or damping 0011 g which has Referring to Fig. 1, the reference Z dethe eifect of producing a time lag suiiicient notes the magnetic system or pot magnet of to smooth out the undesirable wave peaks.

the microphone, while on is the diaphragm If desired, the degree of damping produced thereof and a the form of holder for the movby the coil 3 may be rendered ad ustable by inn coil attached to said diaphragm. connecting the ends of said coil, through leads The whole of this microphone assembly is T, to a variable high resistance 2 instead enclosed in a casing o the space between the of merely short c rculting sa d c011. With 50 pot l and the casing a being filled in with such a'variable resistance in circuit, the tone 1.00

tends to be high pitched and harsh but areduction of the resistance puts more electrical load across the coil 3/ which, when a proper setting for a has been found, produces the desired time lag.

Instead of-using a second coil such as g the form n for the audio-frequency coil w,

may be provided by a light metal ring which, acting as a one-turn coil, will produce damp ing effect-s substantially the same as those set up by the second coil above referred to.

that I claim is:

1. In combination with an organ, an electrical system for amplifying the sound comprising a microphone havingmeans damping the audio-frequency vibrations generated therein; a reproducer connected with the m1- crophone and adapted to magnify the damped vibrations thereto transmitted; and a sound proof container for the microphone con nected with the organ and having a single size-controllable opening disposed toward said organ to admit sound only from the latter.

2. In combination With a organ, an electrical system for amplifying the sound comprising a microphone having means damping the audio-frequency vibrations generated therein; a reproducer connected w th the microphone and adapted to magnify the damped vibrations thereto transmitted; a sound-proof container for the microphone having a single opening disposed toward the organ to admit sound only from the latter; and means for controlling said opening for varying the volume of sound thereby admitted to the microphone.

3. In combination with a source of sound production, an electrical system for ampl1fying the sound comprising a microphone having means damping the audio-frequency vibrations generated therein; a reproducer connected with the microphone and adapted to magnify the vibrations thereto transmitted; a sound-proof container for the microphone having a single opening dlsposed toward said source for admitting sound therefrom to the microphone; and a shutter device operable automatically by an operable part of the sound source for varying the size of said opening.

4-. In combination With a source of sound production, an electrical system for amplifying the sound comprising a microphone hav ing means damping the audio-frequency vibrations generated therein; a reproducer conncted with the microphone and adapted to magnify the vibrations thereto transmitted; a sound-proof container for the microphone having a single opening disposed toward said source to admit sound therefrom to the microphone; and a shutter device cona large pipe organ comprising a microphone having means for damping the audio frequency vibrations generated therein, a reproducer connected with the microphone and adapted to magnify the damped vibrations thereto transmitted, a sound-proof container for the microphone having a single opening disposed toward said organ to admit sound only from the latter, and a shutter device connected with the swells of the organ for automatically varying the size of said opening according to the volume of sound emitted by the organ.

6. In a sound amplifying system as applied to a small organ, the combination with a microphone and a sound reproducer, of a sound-proof box for the microphone, said box being acoustically connected With the organ in a manner effecting a balance between the high and low registers and means automatically operable by a part of the organ for controlling the volume of sound admitted to the box from said organ.

7. A system for amplifying the acoustic.

output of the different instruments selectively of an orchestra, comprising a microphone within a sound-proof container disposed toward the instrument and having a single opening admitting sound therethrough to the microphone, means associated with the microphone for damping the audio-frequency vibrations generated therein so as to temper and clarify sound reproduction, and a reproducer connected with the microphone and adapted to magnify the damped vibrations thereto transmitted by the latter, together With a shutter device actuable to vary the size of the opening of said container for controllingthe volume of sound admitted to the microphone from said instrument.

Signed at London, England, this 10th day of December, 1928 HAROLD GREEN.

nected for automatic operation from the sound source for varying the size of said 

